Abstract Dynamic processes in the accretion flow near black holes produce X-ray flux variability, sometimes quasiperiodic. Determining its physical origin is key to mapping the accretion geometry but remains unresolved. We perform a novel phase-resolved analysis on a newly discovered quasiperiodic oscillation (QPO) in the active galactic nucleus 1ES 1927+654. For the first time in a supermassive black hole (SMBH), we detect a unique “U”-shaped QPO lag–energy spectrum and observe coronal spectral variability over the QPO phase. We find that the QPO is adequately explained by plasma resonant oscillations within a corona. The modeling of the QPO spectral properties reveals that the corona is contracting and confined to regions of only a few gravitational radii near the SMBH, consistent with theoretical predictions for a decreasing QPO period of near 10 minutes. These results present the first observational evidence for an oscillating and contracting compact corona around an SMBH.
Shui et al. (Tue,) studied this question.
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